How should the pipe size of the longest run from the point of delivery be determined?

The correct approach to determining the pipe size of the longest run from the point of delivery involves analyzing both the longest run and the load section. This method ensures that the gas system can efficiently deliver the required volume to the appliances, taking into account the pressure drop that can occur over longer distances.

When calculating the pipe size, it's important to consider the total demand of the appliances served by that particular run, as well as the distance and the characteristics of the pipe being used. This holistic view allows for the selection of a pipe size that maintains adequate pressure and flow rate, ensuring that all appliances operate effectively and safely.

Other methods, such as considering only the appliance requirements or the size of the first section, do not account for the increased resistance and potential pressure drop that occurs in longer runs, which could lead to insufficient gas flow to appliances further downstream. Hence, utilizing the longest run and load section provides a more reliable means of determining the appropriate pipe size.